PROJECT SUMMARY Pulmonary Arterial Hypertension (PAH) is a fatal disease caused by elevated vascular resistance due to lumen-obliterating processes in small pulmonary arteries. To improve clinical outcome, a better understanding regarding the pathogenesis of PAH is desperately needed. Recently we reported that chronic exposure of interleukin-13 (IL-13) in murine lungs, using a transgenic approach (IL-13 Tg), induced impressive smooth muscle cell-driven pulmonary vascular remodeling (PVR) leading to pulmonary hypertension (PH). We further showed that IL-13-induced proliferation of vascular smooth muscle cells in vivo and in vitro is mediated through Arginase2 (Arg2) via IL-13 receptor alpha2 (IL-13Ra2). Also, we observed that IL-13 increased the expression and activity of hypoxic inducible factor1a (HIF1a) via IL-13Ra2, as well, and that IL-13-induced proliferation of human pulmonary artery smooth muscle cell (hPASMC) is significantly decreased with knocking HIF1a gene down. Furthermore, HIF1a regulates Arg2 expression at transcriptional level. These findings implicate the important role of HIF1a in IL-13-induced proliferation of vascular smooth muscle cells. Given that HIF1a is a metabolic switch from oxidative phosphorylation to glycolysis, these findings suggest that IL-13 might induce the Warburg type effect (increased aerobic glycolysis and decreased oxidative phosphorylation in cancer cells leading to proliferation) to stimulate proliferation of vascular smooth muscle cells. Specific Aims We propose the following hypotheses: 1. IL-13 stimulates the proliferation of hPASMC through IL-13Ra2. 2. HIF1a plays a critical role in IL-13-stimulated proliferation of hPASMC via IL-13Ra2. 3. IL-13 regulates the metabolic shift from oxidative phosphorylation to glycolysis via IL-13Ra2, HIF1a and Arg2, thereby inducing PASMC proliferation and PH. Our Aims are to: AIM 1. Define the role of IL-13Ra2 in the development of IL-13-induced PH in vitro and in vivo. AIM 2. Define the role of HIF1a in the generation of the IL-13-IL-13Ra2-induced proliferative phenotypes in PASMC in vitro and in vivo. AIM 3. Define the role of IL-13 in the development of the metabolic shift from oxidative phosphorylation to glycolysis in PASMC in vitro and in vivo. Experimental Approach We will use both in vivo and in vitro approaches using hPASMC and IL-13 Tg mice. To address AIM 1, the pulmonary vascular phenotype will be assessed in IL-13 Tg mice crossed with IL-13Ra2 null mutant compared to IL-13 Tg. Further hPASMC transfected with the specific siRNA of IL-13Ra2 will be treated with IL-13 and proliferation assays will be done. The results will be compared to those from hPASMC transfected with control siRNA. To address AIM 2, HIF1a expression will be examined and compared using Western blot in IL-13- treated hPSAMC with or without knocking the IL-13Ra2 gene down, and IL-13 Tg and IL-13 Tg crossed with IL-13Ra2 null mutant mice. To address AIM 3, lactate levels and oxygen consumption rates in IL-13-stimulated hPASMC will be assessed. A metabolic modifier will be given to IL-13 Tg mice to see whether the metabolic shift in IL-13 Tg through HIF1a alters the pulmonary vascular phenotype in these animals. This work will provide us with a novel insight into the pathogenesis of pulmonary hypertension induced by a complex interaction between immune and metabolic processed in addition to a novel regulatory pathway of HIF1a. This grant proposes a research mentorship program at Yale University under the primary sponsorship of Dr. Jack Elias, a world-renowned investigator in lung inflammation and immunobiology, and Dr. Hyung Joon Chun, an expert in vascular signaling and pharmacology, as a co-mentor. We have also enlisted the expertise of Yale investigators Drs. Gerald Shadel, Patty Lee, William Sessa, Frank Giordano and Chun Geun Lee as advisory committee members to provide scientific and career counseling. The proposed career and research program as outlined will provide an extraordinary scientific environment wherein Dr. Cho can launch her future independent career as a physician-scientist.